“People are more symptomatic from thyroid enlargement than we’ve ever really given them credit for,” Dr. Michael T. Stang of the University of Pittsburgh School of Medicine, the study’s first author, told Reuters Health. “We see a great number of patients, whether they have really big thyroids or even not-so-big thyroids, once they’re removed, they feel much better from a breathing standpoint.”
While physicians have observed that patients’ shortness of breath can improve after thyroidectomy, Dr. Stang and his team note in their report, “the indications for goiter resection remain uncertain, the definition of goiter itself remains controversial, and the precise definition of substernal extension varies by expert.”
Further, they point out, it’s not clear how thyroid enlargement might relate to obstructive sleep apnea (OSA).
To investigate, Dr. Stang and his colleagues looked at 1,081 patients who underwent thyroidectomy, in most cases because they had thyroid nodules larger than 4 centimeters or an indeterminate fine-needle-aspirate biopsy. A total of 197 had positional dyspnea, tracheal compression, or both.
Among the 188 patients with positional dyspnea, 82.4% reported improvement or resolution of their symptoms after thyroidectomy at a mean follow-up of 12.6 months.
Imaging showed tracheal compression in 97.2% of the 151 patients with substernal goiter; their mean tracheal compression was 34%. Among the patients with tracheal compression, 93.5% had positional dyspnea
After patients underwent substernal goiter resection, their positional dyspnea symptoms improved. Gland weight of 100 grams or more, or tracheal compression of at least 35%, “strongly predicted” improvement in shortness of breath, the researchers found.
Thirty-five of the patients had been formally diagnosed with OSA before undergoing surgery, and 31 of them were using continuous positive airway pressure (CPAP). Fourteen of these patients said they were able to stop using CPAP after thyroidectomy, while four reported using it less. In the three OSA patients who underwent a repeat sleep study after thyroidectomy, one showed no improvement in apnea-hypopnea index, one showed an improvement from 53.8 to 28.9, and the third patients’ AHI was reduced from 22.4 to 0.2.
Based on the findings, the researchers state, positional dyspnea combined with tracheal compression of 35% or more in patients with thyroid enlargement is an indication for goiter resection. “Pilot results also support further study of goiter as a correctable cause of snoring and misdiagnosed OSA,” they conclude.
Dr. Herbert Chen of the University of Wisconsin Medical School in Madison co-authored an invited critique on the study. “When a patient presents with dyspnea or shortness of breath,” he told Reuters Health, “I think one of the items in the differential diagnosis has to be thyroid enlargement, and that’s probably not something that pops up on the radar screen of the doctors who see these patients initially.”
“These studies provide data to support what many thyroid surgeons have always intuitively known,” Dr. Chen and his colleague Dr. David Schneider write. “We have all met the poor patient subjected to repeated pulmonary function testing, sleep studies, bothersome constant positive airway pressure equipment, and an endless catalog of symptoms. Finally, an enlarged thyroid is ‘discovered,’ and the patient is referred for surgery.”
While the precise reason for why an enlarged thyroid gland is related to respiratory symptoms “remains elusive,” they add, evaluating the relationship prospectively “would certainly involve expensive preoperative and postoperative sleep studies or pulmonary function testing. We are not sure that is really necessary if we just trust our common sense and the well-done retrospective study reported in this article.”